Solvent independent reference electrodes for use with non-aqueous electrolytes

1. A method for forming a reference electrode for use in electrochemical testing applications, the method comprising:

positioning a porous frit against one end of a hollow tube;

securing the frit and the hollow tube to one another to form an assembly;

boiling the assembly in a solution to remove organic contaminants; and

drying the assembly;

forming a silver sulfide coating on a silver wire to produce a silver sulfide coated silver wire;

filling the hollow tube with a non-aqueous solution; and

inserting at least a portion of the silver sulfide coated silver wire into the non-aqueous solution in the hollow tube.

2. The method of claim 1 , wherein securing the frit and the hollow tube comprises:

arranging a portion of shrink wrap over portions of the frit and the hollow tube; and

heating the portion of shrink wrap, the hollow tube and the frit to shrink the shrink wrap onto the portions of the frit and the hollow tube to form the assembly.

3. The method of claim 2 , wherein heating the portion of shrink wrap comprises heating the portion of shrink wrap to a temperature of about 350° C. for at least three hours.

4. The method of claim 1 , wherein positioning the frit against one end of a hollow tube comprises positioning a glass frit against one end of a hollow glass tube.

5. The method of claim 1 , wherein inserting the at least a portion of the silver sulfide coated silver wire into the non-aqueous solution in the hollow tube comprises using a silver wire having a thickness of about 0.5 mm.

6. The method of claim 5 , wherein forming the reference electrode comprises forming a reference electrode with a volume of no more than about 0.5 mL.

7. The method of claim 6 , wherein securing the hollow tube and the frit to form the assembly comprises securing a hollow tube with a diameter of no more than about 4 mm to the frit, and wherein a ratio of the silver wire diameter to the hollow tube diameter is about 1:8.

8. The method of claim 1 , further comprising:

subsequent to boiling the assembly in a solution to remove organic contaminants and prior to drying the assembly, boiling the assembly in water.

9. The method of claim 8 , wherein boiling the assembly in the solution comprises boiling the assembly in hydrogen peroxide.

10. The method of claim 8 , wherein drying the assembly comprises drying the assembly in an oven at a temperature of about 140° C.

11. The method of claim 1 , wherein forming the silver sulfide coating on the silver wire comprises:

placing a quantity of sulfur on a hot plate;

arranging the silver wire over the sulfur; and

using the hot plate to heat the sulfur to cause sublimation of the sulfur and subsequent reaction with the silver wire, to thus form the silver sulfide coated silver wire.

12. The method of claim 1 , wherein forming a silver sulfide coating on a silver wire comprises:

placing elemental sulfur powder in a vial;

inserting a clean silver wire into the elemental sulfur powder in the vial;

leaving the silver wire in contact with the elemental sulfur powder for a period of at least 24 hours to form the silver sulfide coating on the silver wire; and

removing the silver wire from the elemental sulfur powder and rinsing the silver sulfide coated silver wire to remove any portion of the elemental sulfur powder that did not react to form the silver sulfide coating.

13. The method of claim 1 , wherein forming a silver sulfide coating on a silver wire comprises:

exposing a clean silver wire to a hydrogen sulfide atmosphere containing hydrogen sulfide gas; and

maintaining the clean silver wire in the hydrogen sulfide atmosphere for at least 10 minutes until a silver sulfide coating has formed on a surface of the clean silver wire.

14. The method of claim 1 , further comprising:

measuring a stability of the reference electrode by:

submerging the reference electrode in an ionic liquid solution that contains a redox active couple;

at least one of scanning or cycling a potential in a range where the redox active couple undergoes a redox reaction;

measuring a potential of a redox peak throughout multiple potential cycles; and

using a potential drift of the redox peak to quantify the stability of the reference electrode.

15. A method for forming a reference electrode for use in electrochemical testing applications, the method comprising:

positioning a cylindrical porous frit against one end of a hollow tube, where the hollow tube has a volume of about 0.1-0.5 mL and a diameter of about 4 mm, and the porous frit and the hollow tube have a common outer diameter;

securing the frit to one end of the hollow tube using a portion of flexible material, to form an assembly;

boiling the assembly in a solution to remove organic contaminants;

boiling the assembly in water; and

drying the assembly;

forming a silver sulfide coating on a silver wire to produce a silver sulfide coated silver wire, and wherein the silver wire before forming the silver sulfide coating comprises a diameter of about 0.5 mm, to produce a ratio of the silver wire diameter to the hollow tube diameter of about 1:8;

filling the hollow tube with a non-aqueous solution; and

inserting at least a portion of the silver sulfide coated silver wire into the non-aqueous solution in the hollow tube.

16. The method of claim 15 , wherein securing the frit and the hollow tube comprises:

arranging a portion of shrink wrap over portions of the frit and the hollow tube; and

heating the portion of shrink wrap, the hollow tube and the frit to shrink the shrink wrap onto the portions of the frit and the hollow tube to form the assembly.

17. The method of claim 16 , wherein heating the portion of shrink wrap comprises heating the portion of shrink wrap to a temperature of about 350° C. for at least three hours.

18. The method of claim 15 , wherein boiling the assembly in the solution comprises boiling the assembly in hydrogen peroxide.

19. The method of claim 15 , wherein drying the assembly comprises drying the assembly in an oven at a temperature of about 140° C.

20. A method for forming a reference electrode for use in electrochemical testing applications, the method comprising:

positioning a porous frit against one end of a hollow tube;

securing the frit and the hollow tube to one another to form an assembly;

boiling the assembly in a solution to remove organic contaminants;

boiling the assembly in water; and

drying the assembly;

forming a silver sulfide coating on a silver wire to produce a silver sulfide coated silver wire;

filling the hollow tube with a non-aqueous solution;

inserting at least a portion of the silver sulfide coated silver wire into the non-aqueous solution in the hollow tube.

21. A method for forming a reference electrode for use in electrochemical testing applications, the method comprising:

positioning a porous frit against one end of a hollow tube;

securing the frit and the hollow tube to one another to form an assembly;

forming a silver sulfide coating on a silver wire to produce a silver sulfide coated silver wire;

filling the hollow tube with a non-aqueous solution; and

inserting at least a portion of the silver sulfide coated silver wire into the non-aqueous solution in the hollow tube;

wherein forming a silver sulfide coating on a silver wire includes:

placing elemental sulfur powder in a vial;

inserting a clean silver wire into the elemental sulfur powder in the vial;

leaving the silver wire in contact with the elemental sulfur powder for a period of at least 24 hours to form the silver sulfide coating on the silver wire; and

removing the silver wire from the elemental sulfur powder and rinsing the silver sulfide coated silver wire to remove any portion of the elemental sulfur powder that did not react to form the silver sulfide coating.